1. Field of the Invention
The present invention relates to a substance that can induce interleukin-12 in vivo, and to a medical composition containing the same.
2. Description of the Related Art
Interleukin-12 (IL-12) was originally found as one of cytokinins that can activate NK cells. Subsequent studies revealed that it also promoted growth of and activated T cells that had cytotoxicity specific to tumor cells (Killer T cells), and further it promoted the production of interferon .gamma. (IFN .gamma.) that stimulated activation of killer T cells. Thus IL-12 has attracted attention as a substance effective in treating human cancer patients.
Recently, large-scale production of IL-12 by using a gene manipulation technique was realized in the U.S. (Recombinant IL-12 (rt-IL-12)). Following that, in order to directly deliver IL-12 to cancer cells, a method for directly introducing the IL-12 producing gene into tumor cells, by using gene introduction techniques, has been investigated.
However, sensitivity of rt-IL-12 used in the method is low and administration of a large-amount is needed, for example, to treat human cancer. Such large-amount dosage causes various side effects including fever and inappetence. Besides these serious side effects, several problems regarding this method are pointed out, that is, the gene manipulation procedure is so complicated that it is labor intensive and lacks economical feasibility.
For using IL-12 to prevent tumor growth or cause regression, there are two methods; one is to externally administrate IL-12, and the other is to induce in vivo production of IL-12. Such induced IL-12 does not raise abnormal immune response, thereby resolving intrinsic problems of rt-IL-12. At the same time, such IL-12 is highly effective, thus extensive tumor loss regression effect can be expected. However, before the instant invention an effective substance that could induce IL-12 of its own in vivo had not been found.